Method and Apparatus for Controlling Gas Turbine Combustor

ABSTRACT

An apparatus for controlling a gas turbine combustor having a diffusion combustion burner and a premix combustion burner comprising: a rotating speed detector for detecting a rotating speed of gas turbine, a recorder for recording the detected value of the rotating speed of gas turbine detected by the rotating speed detector, an arithmetic unit for calculating a change with time of the rotating speed of gas turbine in accordance with details of the detected value of the rotating speed of gas turbine recorded in the recorder, and a fuel control unit for judging a starting situation of reduction in the rotating speed of gas turbine on the basis of the change with time of the rotating speed of gas turbine calculated by the arithmetic unit and controlling respectively a fuel flow rate for the diffusion combustion burner to be fed to the diffusion combustion burner installed in the gas turbine combustor and a fuel flow rate for the premix combustion to be fed to the premix combustion burner.

CLAIM OF PRIORITY

The present application claims priority from Japanese patent applicationJP 2010-198518 filed on Sep. 6, 2010, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus forcontrolling a gas turbine combustor.

2. Description of Related Art

In the gas turbine combustor, there are a diffusion combustor and apremix combustor available. The diffusion combustor is a system forseparately feeding and burning fuel and air in a combustion chamber, anda flame is formed in a state close to the stoichiometric ratio of fuelto air, and the local flame temperature rises, so that although thecombustion stability is high, the nitrogen oxide (NOx) emissionincreases.

On the other hand, the premix combustor is a system for premixing fueland air and then feeding and burning them in the combustion chamber, andthe mixing ratio of fuel and air on the flame sheet is lower than thatin the diffusion combustion, and the local flame temperature is lowered,so that the emission of NOx can be reduced.

As general use of a low NOx combustor, at the time of a low loadoperation from start up to acceleration, the diffusion combustion ofhigh combustion stability is used and at the time of the base loadoperation from a partial load, the diffusion combustion of highcombustion stability and the premix combustion capable of reducing theNOx emission are combined, thus the combustion stability and thereduction in the NOx discharging rate are compatible with each other.

When using the gas turbine for power generation, the gas turbine needsto withstand a load dump when the load operation state is transferred tothe no-load operation state due to separation of the generator from thegas turbine. The load dump is to urgently separate the generator andturbine from each other from some cause and in this case, the gasturbine needs to immediately enter the full speed no-load operationstate.

Immediately after the load dump, the rotating speed of the gas turbineincreases. If the rotating speed of the gas turbine increases to thelimit value or higher, there is a concern that it may lead to damage tothe compressor or turbine and it is necessary to promptly reduce thefuel flow rate to the minimum limit capable of maintaining the flame bythe gas turbine combustor, thereby suppressing an increase in therotating speed of the gas turbine.

Due to the increase in the rotating speed of the gas turbine incorrespondence to the load dump, the flow rate of compressed air flowinginto the gas turbine combustor increases, and the fuel flow rate reducessuddenly, so that the inner state of the gas turbine combustor istransiently greatly changed. Therefore, in the gas turbine combustor,high combustion stability is required, and when reducing the fuel flowrate at the time of load dump, so as to dump the fuel for premixcombustion, thereby switch to the independent diffusion combustion, thefuel flow rate is controlled.

In Japanese Patent Laid-open No. Hei 10 (1998)-169467 of a prior art, atthe time of load dump of the gas turbine, an art capable of switchingthe premix combustion to the independent diffusion combustion withoutdelay of ignition is disclosed.

-   Patent Document 1: Japanese Patent Laid-open No. Hei 10(1998)-169467

SUMMARY OF THE INVENTION

The regulation and social demands on the environment become stronger dayby day and also in the gas turbine combustor, a further reduction in theNOx emission is required. In the base load operation state from thepartial load of the gas turbine, the combustion of the gas turbinecombustor is switched to the mixed combustion of the diffusioncombustion and premix combustion, thus the NOx emission rate can bereduced.

Further, in the gas turbine, to suppress the increase in the rotatingspeed due to the load dump, the fuel for the premix combustion is dumpedat the time of load dump and so as to switch to the independentdiffusion combustion, the fuel flow rate fed to the gas turbinecombustor is controlled.

In Japanese Patent Laid-open No. Hei 10 (1998)-169467 aforementioned, atthe time of load dump of the gas turbine, the art capable of switchingthe premix combustion to the independent diffusion combustion withoutdelay of ignition is disclosed, though the time required to return fromthe load dump to the ordinary operation state depends upon the cause ofthe load dump and there is a possibility that the full speed no-loadoperation state after the load dump may be held for many hours.

When the full speed no-load operation state after the load dump is heldfor many hours, the independent diffusion combustion state of a high NOxemission is continued, so that an increase in the NOx emission due tothe full speed no-load operation state after the load dump causes aproblem.

An object of the present invention is to provide a method and anapparatus for controlling a gas turbine combustor capable of ensuringcombustion stability immediately after load dump of the gas turbine andreducing the NOx emission due to full speed no-load operation after theload dump.

An apparatus for controlling a gas turbine combustor having a diffusioncombustion burner and a premix combustion burner comprising: a rotatingspeed detector for detecting a rotating speed of gas turbine, a recorderfor recording the detected value of the rotating speed of gas turbinedetected by the rotating speed detector, an arithmetic unit forcalculating a change with time of the rotating speed of gas turbine inaccordance with details of the detected value of the rotating speed ofgas turbine recorded in the recorder, and a fuel control unit forjudging a starting situation of reduction in the rotating speed of gasturbine on the basis of the change with time of the rotating speed ofgas turbine calculated by the arithmetic unit and controllingrespectively a fuel flow rate for the diffusion combustion burner to befed to the diffusion combustion burner installed in the gas turbinecombustor and a fuel flow rate for the premix combustion to be fed tothe premix combustion burner.

An apparatus for controlling a gas turbine combustor having a diffusioncombustion burner and a premix combustion burner comprising: a detectorfor detecting a rotating speed of gas turbine, a recorder for recordingthe detected value of the rotating speed of gas turbine detected by therotating speed detector, an arithmetic unit for calculating a changewith time of the rotating speed of gas turbine in accordance withdetails of the detected value of the rotating speed of gas turbinerecorded in the recorder, a bleed valve opening angle detector fordetecting an opening angle of a compressor bleed valve installed in acompressor, a logic circuit for checking a value of the change with timeof the rotating speed of gas turbine calculated by the arithmetic unitand an opening angle signal of the bleed valve detected by the bleedvalve opening angle detector, and a fuel control unit for respectivelycontrolling a fuel flow rate for the diffusion combustion burner to befed to the diffusion combustion burner installed in the gas turbinecombustor and a fuel flow rate for the premix combustion to be fed tothe premix combustion burner so as to switch a combustion state of thegas turbine combustor from independent diffusion combustion by thediffusion combustion burner to mixed combustion of diffusion combustionand premix combustion by the diffusion combustion burner and the premixcombustion burner on the basis of check results by the logic circuit.

An apparatus for controlling a gas turbine combustor having a diffusioncombustion burner and a premix combustion burner comprising: a fuelcontrol unit for respectively controlling a fuel flow rate for thediffusion combustion burner to be fed to the diffusion combustion burnerinstalled in the gas turbine combustor and a fuel flow rate for thepremix combustion to be fed to the premix combustion burner so as toswitch a combustion state of the gas turbine combustor from independentdiffusion combustion by the diffusion combustion burner to mixedcombustion of diffusion combustion and premix combustion by thediffusion combustion burner and the premix combustion burner on thebasis of a signal transmitted from a timer circuit, which is installedto transmit a signal for controlling the fuel control unit after apredetermined period of time after receipt of a load dump signal of gasturbine, after a predetermined period of time.

A method for controlling a gas turbine combustor including a diffusioncombustion burner and a premix combustion burner, comprising the stepsof: detecting a rotating speed of gas turbine, recording the detectedvalue of the rotating speed of gas turbine, calculating a change withtime of the rotating speed of gas turbine in accordance with details ofthe recorded detected value of the rotating speed of gas turbine,judging a starting situation of reduction in the rotating speed of gasturbine on the basis of the calculated change with time of the rotatingspeed of gas turbine, and regulating a fuel flow rate fed to the gasturbine combustor controls respectively a fuel flow rate for thediffusion combustion burner to be fed to the diffusion combustion burnerinstalled in the gas turbine combustor and a fuel flow rate for thepremix combustion to be fed to the premix combustion burner.

A method for controlling a gas turbine combustor including a diffusioncombustion burner and a premix combustion burner, comprising the stepsof: detecting a rotating speed of a gas turbine, recording the detectedvalue of the rotating speed of gas turbine, calculating a change withtime of the rotating speed of gas turbine in accordance with details ofthe recorded detected value of the rotating speed of gas turbine,detecting an opening angle of a compressor bleed valve installed in acompressor, and regulating a fuel flow rate fed to the gas turbinecombustor on the basis of check results of a calculated value of thechange with time of the rotating speed of gas turbine and a detectedopening angle signal of the bleed valve respectively controls a fuelflow rate for the diffusion combustion burner to be to the diffusioncombustion burner installed in the gas turbine combustor and a fuel flowrate for the premix combustion to be fed to the premix combustion burnerso as to switch a combustion state of the gas turbine combustor fromindependent diffusion combustion by the diffusion combustion burner tomixed combustion of the diffusion combustion and the premix combustionby the diffusion combustion burner and the premix combustion burner.

A method for controlling a gas turbine combustor having a diffusioncombustion burner and a premix combustion burner, comprising the stepsof: controlling a fuel flow rate for the diffusion combustion burner tobe fed to the diffusion combustion burner installed in the gas turbinecombustor and a fuel flow rate for the premix combustion to be fed tothe premix combustion burner respectively so as to switch a combustionstate of the gas turbine combustor from independent diffusion combustionby the diffusion combustion burner to mixed combustion of the diffusioncombustion and the premix combustion by the diffusion combustion burnerand the premix combustion burner on the basis of a signal transmittedfrom a timer circuit, which is installed to transmit a signal forcontrolling the fuel control unit after a predetermined period of timeafter receipt of a load dump signal of gas turbine, after apredetermined period of time.

According to the present invention, a method and an apparatus forcontrolling a gas turbine combustor capable of ensuring combustionstability immediately after load dump of the gas turbine and reducingthe NOx emission due to full speed no-load operation after the load dumpcan be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the gas turbine unit including the gasturbine combustor that is the first embodiment of the present invention,

FIG. 2 is a characteristic diagram showing the fuel flow rate of the gasturbine combustor that is the first embodiment of the present inventionand the load of the gas turbine,

FIG. 3 is a characteristic diagram showing the changes with time of thefuel flow rate of the diffusion combustion burner, the fuel flow rate ofthe premix combustion burner, the rotating speed of the gas turbine, andthe NOx emission at the time of load dump in the first embodiment of thepresent invention,

FIG. 4 is a block diagram of the gas turbine unit including the gasturbine combustor that is the second embodiment of the presentinvention,

FIG. 5 is a characteristic diagram showing the changes with time of thefuel flow rate of the diffusion combustion burner, the fuel flow rate ofthe premix combustion burner, the rotating speed of the gas turbine, andthe NOx emission at the time of load dump in the second embodiment ofthe present invention,

FIG. 6 is a block diagram of the gas turbine unit including the gasturbine combustor that is the third embodiment of the present invention,

FIG. 7 is a characteristic diagram showing the changes with time of thefuel flow rate of the diffusion combustion burner, the fuel flow rate ofthe premix combustion burner, the rotating speed of the gas turbine, andthe NOx emission at the time of load dump in the third embodiment of thepresent invention,

FIG. 8 is a characteristic diagram showing the relationship between therotating speed of the gas turbine and the fuel flow ratio at the time ofload dump in the third embodiment of the present invention,

FIG. 9 is a block diagram of the gas turbine unit including the gasturbine combustor that is the fourth embodiment of the presentinvention,

FIG. 10 is a characteristic diagram showing the rotating speed of thegas turbine, the opening angle of the bleed valve, and the flow rate ofcompressed air at the time of load dump in the fourth embodiment of thepresent invention,

FIG. 11 is a block diagram of the gas turbine unit including the gasturbine combustor that is the fifth embodiment of the present invention,

FIG. 12 is a block diagram of the gas turbine unit including the gasturbine combustor which is the sixth embodiment of the presentinvention, and

FIG. 13 is a characteristic diagram showing the fuel flow rate, therotating speed of the low-pressure turbine, and the rotating speed ofthe high-pressure turbine at the time of load dump in the sixthembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A control apparatus for controlling a gas turbine combustor that is anembodiment of the present invention will be explained below withreference to the accompanying drawings.

When using the gas turbine for power generation, the gas turbine needsto withstand the load dump of the gas turbine transferring from the loadoperation state to the no-load operation state by separating thegenerator from the gas turbine.

At the time of the load dump of the gas turbine, it is necessary topromptly reduce the fuel flow rate down to the minimum limit at whichthe gas turbine combustor can maintain the flame and prevent thecompressor and gas turbine from damage due to an increase in therotating speed of the gas turbine up to the limit value or higher.

Due to the increase in the rotating speed of the gas turbine incorrespondence to the load dump, the flow rate of compressed air flowinginto the gas turbine combustor increases, and the fuel flow rate reducessuddenly, so that the inner state of the gas turbine combustor isgreatly changed transiently. Therefore, the gas turbine combustor isrequired for high combustion stability, so that when reducing the fuelflow rate at the time of the load dump of the gas turbine, fuel iscontrolled so as to dump the premix fuel and switch to the independentdiffusion combustion.

On the other hand, if the combustion of the gas turbine combustor isswitched from the premix combustion to the independent diffusioncombustion, the NOx emission due to the full speed no-load operationafter the load dump increases.

Therefore, the control apparatus of the gas turbine combustor of thepresent invention includes the detector for detecting the rotating speedof the gas turbine, the recorder for recording a signal of the detector,the arithmetic unit for calculating the change with time of the rotatingspeed from the information of the recorder, and the fuel control unit,upon receipt of a signal from the arithmetic unit, for controlling thefuel flow rates to be fed to the diffusion combustion burner and premixcombustion burner of the gas turbine combustor and is structured so asto output an operation signal to the fuel control unit from thearithmetic unit if the rotating speed of the gas turbine increased fromthe rated rotating speed due to the load dump of the gas turbine startsto reduce from the increased rotating speed of the gas turbine andcontrol the fuel flow rate fed to the gas turbine combustor so as toswitch the independent diffusion combustion to the mixed combustion ofthe diffusion combustion and premix combustion.

The control apparatus of the gas turbine combustor is structured asmentioned above, thus if the rotating speed of the gas turbine increasedfrom the rated rotating speed after the load dump of the gas turbinestarts to reduce, the independent diffusion combustion can be promptlyswitched to the mixed combustion of the diffusion combustion and premixcombustion, so that the NOx emission due to the full speed no-loadoperation after the load dump can be reduced.

Embodiment 1

The control apparatus of the gas turbine combustor and the controlmethod of the gas turbine combustor of the first embodiment of thepresent invention will be explained by referring to FIGS. 1 to 3.

FIG. 1 shows an entire drawing of the gas turbine unit for powergeneration having the gas turbine combustor which is the firstembodiment of the present invention, and the gas turbine unit includes acompressor 1, a gas turbine combustor 2, and a turbine 3, and by theoutput of the turbine 3, a generator 4 is rotated, thus power isobtained.

Compressed air 100 compressed by the compressor 1 flows into the gasturbine combustor 2 via a diffuser 5 and passes between an outer sleeve6 and a combustor liner 7.

A part of the compressed air 100 flows into a combustion chamber 8 ofthe gas turbine combustor 2 as cooling air 101 of the combustor liner 7.The compressed air 100 not used as cooling air 101 respectively flowsinto a diffusion combustion burner 9 arranged on the upstream side ofthe combustor 2 and on the axial center side of the combustor and apremix combustion burner 10 arranged on the outer circumference side ofthe diffusion combustion burner 9 as combustion air.

The diffusion combustion burner 9 installed in the gas turbine combustor2 includes a fuel nozzle 11 for the diffusion combustion burner and aswirler 12. The compressed air 100 flowing in the diffusion combustionburner 9 is swirled by the swirler 12 as diffusion combustion air 102,thereby flows into the combustion chamber 8, burns diffusion burner fuelinjected from the fuel nozzle 11 for the diffusion combustion burner,and forms a diffusion flame 103 in the combustion chamber 8.

The premix combustion burner 10 installed in the gas turbine combustor 2respectively includes a plurality of fuel nozzles 13 for the premixburner and a flame stabilizer 14. The compressed air 100 flowing in thepremix combustion burner 10 is mixed and burnt with the premix burnerfuel injected from the premix burner fuel nozzles 13 as premixcombustion air 104 and forms a premix flame 105 in the combustionchamber 8 on the downstream side of the flame stabilizer 14.

High-temperature combustion gas 106 generated by the diffusion flame 103and the premix flame 105 in the combustion chamber 8 passes through atransition piece 15 installed on the downstream side of the gas turbinecombustor 2 and flows into the turbine 3. The combustion gas 106 drivesthe turbine 3, permits the generator 4 connected to the turbine 3 torotate, takes out electric power, and then is discharged from theturbine 3 via the exhaust duct.

The fuel fed to the gas turbine combustor 2 is fed through a diffusioncombustion burner fuel system 17 and a premix combustion burner fuelsystem 18 which branch from a fuel main pipe 16. The fuel main pipe 16,the diffusion combustion burner fuel system 17, and the premixcombustion burner fuel system 18 respectively include a dump valve 19and a control valve 20, thus the ratio of the fuel flow fed to thediffusion combustion burner fuel system 17 and the premix combustionburner fuel system 18 can be controlled.

FIG. 2 shows the relationship between the gas turbine load of the gasturbine combustor 2 of this embodiment and the fuel flow rates ofdiffusion combustion burner fuel 17 a fed to the diffusion combustionburner fuel system 17 and premix combustion burner fuel 18 a fed to thepremix combustion burner fuel system 18.

As shown in FIG. 2, under the operation condition of a low gas turbineload, the diffusion combustion burner fuel 17 a is fed to the diffusioncombustion burner fuel system 17, thereby the gas turbine combustor 2 isswitched to the independent diffusion combustion, thus the combustionstability is improved. Under the operation condition of a high gasturbine load, the diffusion combustion burner fuel 17 a and the premixcombustion burner fuel 18 a are respectively fed to the diffusioncombustion burner fuel system 17 and the premix combustion burner fuelsystem 18, and the mixed combustion of the diffusion combustion andpremix combustion is realized, thus the NOx emission can be reduced.

FIG. 3 shows the changes with time of the diffusion combustion burnerfuel flow rate 17 a and the premix combustion burner fuel flow rate 18 awhich are fed to the diffusion combustion burner fuel system 17 and thepremix combustion burner fuel system 18, the rotating speed of the gasturbine, and the NOx emission generated in the gas turbine combustor 2at the time of the load dump of the gas turbine in the control apparatusof the gas turbine combustor 2 of this embodiment.

As shown in FIG. 3 as a rotating speed of the gas turbine, if the loaddump of the gas turbine occurs, the rotating speed of the gas turbineincreases. If the rotating speed of the gas turbine increasesexcessively, there is a possibility that the compressor 1 or the turbine3 may be damaged, so it is desirable to suppress the rotating speed ofthe gas turbine to about 110% of the rated speed at its maximum.Therefore, it is necessary to detect a load dump signal of the gasturbine, simultaneously reduce the fuel flow rate fed to the gas turbinecombustor 2 down to the minimum limit at which the gas turbine combustor2 can maintain the flame, and suppress the rotating speed of the gasturbine from increasing.

Therefore, in the control apparatus of the gas turbine combustor 2 ofthis embodiment, as shown in FIG. 3 as the diffusion combustion burnerfuel flow rate 17 a and the premix combustion burner fuel flow rate 18a, if the occurrence of the load dump of the gas turbine is detected bythe load dump signal of the gas turbine, the feed of the premixcombustion burner fuel 18 a via the premix combustion burner fuel system18 for feeding to the gas turbine combustor 2 is dumped and with respectto the fuel, only the feed of the diffusion combustion burner fuel 17 avia the diffusion combustion burner fuel system 17 is performed, and theindependent diffusion combustion is switched, thus even at the fuel flowrate of the minimum limit, the combustion stability of the gas turbinecombustor 2 is ensured. The fuel flow rate fed to the gas turbinecombustor 2 is reduced, thus the increased rotating speed of the gasturbine due to the load dump is slowly reduced to the rated rotatingspeed.

In the control apparatus of the gas turbine combustor 2 of thisembodiment, as shown in FIG. 1, the rotating speed of the gas turbine isdetected by a rotating speed detector 200 for detecting the rotatingspeed of the gas turbine, and a detection signal of the rotating speedof the gas turbine which is detected by the rotating speed detector 200is transmitted to a rotating speed recorder 201, and the information ofthe rotating speed of the gas turbine is preserved by the rotating speedrecorder 201. And, the information of the rotating speed of the gasturbine preserved in the rotating speed recorder 201 is sent to arotating speed trend arithmetic unit 202 and by the rotating speed trendarithmetic unit 202, the change with time of the rotating speed of thegas turbine is calculated.

The rotating speed trend arithmetic unit 202 detects it by calculatingthe trend of the change of the rotating speed of the gas turbine on thebasis of the value of the rotating speed of the gas turbine recorded inthe rotating speed recorder 201 that the rotating speed of the gasturbine increased from the rated rotating speed immediately after theload dump which occurs in the gas turbine starts to reduce from theonce-increased rotating speed of the gas turbine, thereby judges theswitching of the combustion form of the gas turbine combustor 2.

And, the control apparatus is structured so that when it is detected bythe rotating speed trend arithmetic unit 202 that the once-increasedrotating speed of the gas turbine starts to reduce, the rotating speedtrend arithmetic unit 202 outputs an instruction signal to a fuelcontrol unit 203 for controlling the flow rate of the fuel to be fed tothe gas turbine combustor 2 and the combustion form of the gas turbinecombustor 2 is switched from the independent diffusion combustion to themixed combustion of the diffusion combustion and premix combustion bythe fuel control unit 203.

When the rotating speed of the gas turbine increased due to the loaddump starts to reduce, the reduction of the rotating speed of the gasturbine is detected by the rotating speed trend arithmetic unit 202, andthe fuel control unit 203 receiving the instruction signal for switchingthe combustion form of the gas turbine combustor 2 from the independentdiffusion combustion to the mixed combustion of the diffusion combustionand premix combustion from the rotating speed trend arithmetic unit 202,so as to switch the combustion form of the gas turbine combustor 2 fromthe independent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion, controls so as to reduce thediffusion combustion burner fuel flow rate 17 a which is fed to thediffusion combustion burner 9 of the gas turbine combustor 2 via thediffusion combustion burner fuel system 17 and increase the premixcombustion burner fuel flow rate 18 a which is fed to the premixcombustion burner 10 via the premix combustion burner fuel system 18.

In the state that the rotating speed of the gas turbine increased fromthe rated rotating speed due to the load dump of the gas turbine startsto reduce from the increased rotating speed of the gas turbine, thetransient unstable state due to the load dump is almost settled and evenif the combustion form of the gas turbine combustor 2 is switched fromthe independent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion, the combustion stability ofthe gas turbine combustor 2 can be kept.

After the combustion form of the gas turbine combustor 2 is switched tothe mixed combustion of the diffusion combustion and premix combustion,the fuel flow rate is regulated and the gas turbine is controlled so asto enter the full speed no-load operation. By executing such fuelcontrol, in the full speed no-load operation state after the load dumpof the gas turbine, the NOx emission generated from the gas turbinecombustor 2 can be reduced.

Further, in the aforementioned control apparatus of the gas turbinecombustor 2 of this embodiment, the reliability of the gas turbinecombustor 2 can be improved. Namely, in the diffusion combustion of thegas turbine combustor 2, a flame is formed in a mixing state close tothe stoichiometric ratio of fuel to air, so that compared with thepremix combustion, a local flame temperature becomes high.

Therefore, when the independent diffusion combustion of the gas turbinecombustor 2 is continued in the full speed no-load operation state afterthe load dump of the gas turbine, there is a possibility that the metaltemperature of the diffusion burner 9 of the gas turbine combustor 2 mayrise.

Therefore, in the control apparatus of the gas turbine combustor 2 ofthis embodiment, when the rotating speed of the gas turbine increasedfrom the rated rotating speed after the load dump of the gas turbinestarts to reduce, as mentioned above, the combustion form of the gasturbine combustor 2 is promptly switched from the independent diffusioncombustion to the mixed combustion of the diffusion combustion andpremix combustion, so that a heat load generated by combustion can bediffused to the diffusion combustion burner 9 and the premix combustionburner 10.

As a result, in the control apparatus of the gas turbine combustor 2 ofthis embodiment, when the rotating speed of the gas turbine increasedfrom the rated rotating speed after the load dump of the gas turbinestarts to reduce, the combustion form of the gas turbine combustor 2 isswitched from the independent diffusion combustion to the mixedcombustion of the diffusion combustion and premix combustion, thus afterignition of the premix combustion burner 10, the metal temperature ofthe diffusion combustion burner 9 is reduced and even in the full speedno-load operation state, the metal temperature of the diffusioncombustion burner 9 can be suppressed low, so that the reliability ofthe diffusion combustion burner 9 can be improved.

Further, the temperature of the premix combustion burner 10 rises whenthe combustion form is switched from the independent diffusioncombustion to the mixed combustion of the diffusion combustion andpremix combustion, though the premix combustion burner fuel flow rate 18a fed to the premix combustion burner 10 via the premix combustionburner fuel system 18 is sufficiently low compared with the rated loadcondition, so that the metal temperature of the premix combustion burner10 is low and the gas turbine combustor 2 creates no trouble inreliability.

According to this embodiment, a method and an apparatus for controllinga gas turbine combustor capable of ensuring combustion stabilityimmediately after the load dump of the gas turbine and reducing the NOxemission due to the full speed no-load operation after the load dump canbe realized.

Embodiment 2

Next, the control apparatus of the gas turbine combustor and the controlmethod of the gas turbine combustor of the second embodiment of thepresent invention will be explained by referring to FIGS. 4 and 5. Thecontrol apparatus of the gas turbine combustor 2 of the secondembodiment of the present invention is the same as that of the gasturbine combustor 2 of the first embodiment shown in FIGS. 1 to 3 in thebasic constitution, so that the explanation common to the two is omittedand only the different portions will be explained below.

FIG. 4 shows an entire drawing of the gas turbine unit for powergeneration including the gas turbine combustor 2 which is the secondembodiment of the present invention and the control apparatus of the gasturbine combustor 2 of this embodiment, in addition to the constitutionof the gas turbine combustor 2 of the first embodiment, is structured soas to install a rotating speed comparison arithmetic unit 204 forcomparing a set switching rotating speed with information of therecorder 201 for recording the rotating speed of the gas turbine and alogic circuit 205 for deciding signals of the rotating speed trendarithmetic unit 202 and the rotating speed comparison arithmetic unit204.

In the fuel control method by the control apparatus of the gas turbinecombustor 2 of the first embodiment, when the rising width of therotating speed at the time of the load dump of the gas turbine is wide,under the condition that the rotating speed of the gas turbine is highand the air flow rates of the compressed air 100 and the premixcombustion air 104 which flow into the gas turbine combustor 2 are high,the combustion form of the gas turbine combustor 2 is switched from theindependent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion. Therefore, at the time ofignition of the premix flame 105 formed in the combustion chamber 8 ofthe gas turbine combustor 2, the premix flame 105 becomes unstabletransiently and there is a possibility of flame loss.

Therefore, the control apparatus of the gas turbine combustor 2 of thisembodiment is structured so as to install the rotating speed comparisonarithmetic unit 204 for comparing the switching rotating speed forswitching the combustion form from the independent diffusion combustionto the mixed combustion of the diffusion combustion and premixcombustion with the information of the rotating speed of the gas turbinerecorded in the recorder 201 and the logic circuit 205 for decidingsignals of the rotating speed trend arithmetic unit 202 and the rotatingspeed comparison arithmetic unit 204.

FIG. 5 shows the changes with time of the diffusion combustion burnerfuel flow rate 17 a and the premix combustion burner fuel flow rate 18 awhich are fed to the diffusion combustion burner fuel system 17 and thepremix combustion burner fuel system 18, the rotating speed of the gasturbine, and the NOx emission generated in the gas turbine combustor 2at the time of load dump of the gas turbine in the control apparatus ofthe gas turbine combustor 2 of this embodiment.

In FIG. 5, in the control apparatus of the gas turbine combustor 2 ofthis embodiment, the rotating speed comparison arithmetic unit 204compares a preset switching rotating speed φ_(p) with the information ofthe rotating speed of the recorder 201 and when the rotating speed ofthe gas turbine increased after the load dump reduces to the switchingrotating speed φ_(p) or lower, transmits a signal to the logic circuit205.

The switching rotating speed φ_(p) is within the range from the ratedrotating speed to 110% of the rated rotating speed and it is desirableto set the rotating speed of the gas turbine so that even if thecombustion form of the gas turbine combustor 2 is switched from theindependent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion, the premix flame 105 formedin the combustion chamber 8 of the gas turbine combustor 2 burns stably.

The logic circuit 205 decides the signals output from the rotating speedtrend arithmetic unit 202 and the rotating speed comparison arithmeticunit 204 and only upon receipt of both of an output signal from therotating speed trend arithmetic unit 202 when the rotating speed of thegas turbine which is increased once due to the load dump starts toreduce and a signal of the rotating speed of the gas turbine of theswitching rotating speed φ_(p) or lower output from the rotating speedcomparison arithmetic unit 204, transmits an operation signal from thelogic circuit 205 to the fuel control unit 203.

The fuel control unit 203 receives the operation signal from the logiccircuit 205 and so the combustion form of the gas turbine combustor 2 isswitched from the independent diffusion combustion to the mixedcombustion of the diffusion combustion and premix combustion, controlsso as to reduce the diffusion combustion burner fuel flow rate 17 awhich is fed via the diffusion combustion burner fuel system 17 andincrease the premix combustion burner fuel flow rate 18 a which is fedvia the premix combustion burner fuel system 18.

The control apparatus of the gas turbine combustor 2 of this embodimentis structured as mentioned above, thus when the rising width of therotating speed of the gas turbine at the time of the load dump of thegas turbine is wide, after the rotating speed of the gas turbine reducesdown to the switching rotating speed φ_(p), the combustion form of thegas turbine combustor 2 is switched from the independent diffusioncombustion to the mixed combustion of the diffusion combustion andpremix combustion, so that the premix flame 105 formed in the combustionchamber 8 of the gas turbine combustor 2 can be ignited stably and canbe prevented from flame loss.

According to this embodiment, a method and an apparatus for controllinga gas turbine combustor capable of ensuring combustion stabilityimmediately after the load dump of the gas turbine and reducing the NOxemission due to the full speed no-load operation after the load dump canbe realized.

Embodiment 3

Next, the control apparatus of the gas turbine combustor and the controlmethod of the gas turbine combustor of the third embodiment of thepresent invention will be explained by referring to FIGS. 6 and 7. Thecontrol apparatus of the gas turbine combustor 2 of the third embodimentof the present invention is the same as that of the gas turbinecombustor 2 of the first embodiment shown in FIGS. 1 to 3 in the basicconstitution, so that the explanation common to the two is omitted andonly the different portions will be explained below.

FIG. 6 shows an entire drawing of the gas turbine unit for powergeneration including the gas turbine combustor 2 which is the thirdembodiment of the present invention and the gas turbine combustor 2 ofthis embodiment, in addition to the constitution of the gas turbinecombustor 2 of the first embodiment, is structured so as to install aswitching rotating speed arithmetic unit 206 for calculating therotating speed of the gas turbine to switch the combustion form of thegas turbine combustor 2 from the independent diffusion combustion to themixed combustion of the diffusion combustion and premix combustion fromthe information of the recorder 201 for recording the rotating speed ofthe gas turbine after the load dump of the gas turbine.

FIG. 7 shows the changes with time of the diffusion combustion burnerfuel flow rate 17 a and the premix combustion burner fuel flow rate 18 awhich are fed via the diffusion combustion burner fuel system 17 and thepremix combustion burner fuel system 18 at the time of load dump of thegas turbine in the control apparatus of the gas turbine combustor 2 ofthis embodiment, the rotating speed of the gas turbine, and the NOxemission generated in the gas turbine combustor 2.

As shown in FIG. 7, in the control apparatus of the gas turbinecombustor 2 of this embodiment, the rotating speed of the gas turbineincreased from the rated rotating speed in correspondence to the loaddump of the gas turbine, if the fuel flow rate fed to the gas turbinecombustor 2 reduces, starts to reduce.

Therefore, in the control apparatus of the gas turbine combustor 2 ofthis embodiment, if it is detected by the rotating speed trendarithmetic unit 202 that the rotating speed of the gas turbine increasedimmediately after the load dump of the gas turbine starts to reduce fromthe rated rotating speed, a signal is transmitted from the rotatingspeed trend arithmetic unit 202 to the switching rotating speedarithmetic unit 206.

The switching rotating speed arithmetic unit 206 receiving the signal ofdetecting that the rotating speed of the gas turbine starts to reducefrom the rotating speed trend arithmetic unit 202, by a built-inarithmetic unit, from the maximum rotating speed φ_(max) of the gasturbine recorded in the rotating speed recorder 201, on the basis ofFormulas (1) and (2) indicated below, calculates a fuel controlswitching rotating speed φ_(c).

By the calculator built in the switching rotating speed arithmetic unit206, the fuel control switching rotating speed φ_(c) is calculated byFormula (1) indicated below.

φ_(c)=φ_(fs)+⊖×(φ_(max)−φ_(fs))  (1)

In Formula (1), φ_(max) indicates a maximum rotating speed after theload dump and φ_(fs) indicates a rated rotating speed. α indicates aconstant and it is a value within the range indicated in Formula (2).

0≦α<1  (2)

The switching rotating speed arithmetic unit 206 transmits the fuelcontrol switching rotating speed φ_(c) calculated by the built-incalculator on the basis of Formulas (1) and (2) to the fuel control unit203 as information of the switching rotating speed φ_(c).

The fuel control unit 203 receiving the information from the switchingrotating speed arithmetic unit 206, in the switching rotating speedφ_(c), so that the switching of the combustion form of the gas turbinecombustor 2 from the independent diffusion combustion to the mixedcombustion of the diffusion combustion and premix combustion iscompleted, as shown in FIG. 7, in accordance with the reduction in therotating speed of the gas turbine, controls so as to reduce thediffusion combustion burner fuel flow rate 17 a which is fed via thediffusion combustion burner fuel system 17 of the gas turbine combustor2 and increase the premix combustion burner fuel flow rate 18 a which isfed via the premix combustion burner fuel system 18 of the gas turbinecombustor 2.

In the control apparatus of the gas turbine combustor 2 of thisembodiment, a fuel flow ratio F_(d) of the diffusion combustion burnerfuel fed to the diffusion combustion burner fuel system 17 and a fuelflow ratio F_(p) of the diffusion combustion burner fuel fed to thepremix combustion burner fuel system 18, using the maximum rotatingspeed φ_(max), the fuel control switching rotating speed φ_(c), therotating speed φ detected by the rotating speed detector 200, and a fuelflow ratio F_(d1) of the diffusion combustion burner fuel afterswitching, are calculated from Formulas (3), (4), and (5) indicatedbelow.

-   -   Fuel flow ratio of diffusion combustion burner fuel: F_(d) (%)        (φ_(c)<φ≦φ_(max))

F _(d)=(φ−φ_(c))/(φ_(max)−φ_(c))×(100−F _(d1))+F _(d1)  (3)

-   -   Fuel flow ratio of diffusion combustion burner fuel: F_(d) (%)        (φ_(fs)≦φ≦φ_(c))

F _(d) =F _(d1)  (4)

-   -   Fuel flow ratio of premix combustion burner fuel: F_(p) (%)

F _(p)=100−F _(d)  (5)

The relationship of the rotating speed of the gas turbine to the fuelflow ratios of the diffusion combustion burner fuel and premixcombustion burner fuel is shown in FIG. 8.

The control apparatus of the gas turbine combustor 2 of this embodimentis structured as mentioned above, thus the reliability when switchingthe combustion form of the gas turbine combustor 2 from the independentdiffusion combustion to the mixed combustion of the diffusion combustionand premix combustion can be improved.

When switching the combustion form of the gas turbine combustor 2, ifthe operation of closing the control valve 20 of the diffusioncombustion burner fuel system 17 for feeding the diffusion combustionburner fuel to the diffusion combustion burner 9 is faster than theoperation of opening the control valve 20 of the premix combustionburner fuel system 18 for feeding the premix combustion burner fuel tothe premix burner 10 of the gas turbine combustor 2, for the flow rateof the compressed air 100 for the rotating speed of the gas turbine, thepremix combustion ratio is increased transiently, and the premix flame105 formed in the combustion chamber 8 of the gas turbine combustor 2becomes unstable, and there is a possibility of flame loss.

Therefore, the control apparatus of the gas turbine combustor 2 of thisembodiment, by use of the aforementioned constitution, in accordancewith the rotating speed of the gas turbine, switches the combustion formof the gas turbine combustor 2 from the independent diffusion combustionto the mixed combustion of the diffusion combustion and premixcombustion, so that when the rotating speed of the gas turbine is high,the diffusion combustion ratio of high stability increases, and theflame stability is ensured, and when the rotating speed of the gasturbine reduces, the premix combustion ratio increases, thus the NOxemission generated by the gas turbine combustor 2 can be reduced.

According to this embodiment, a method and an apparatus for controllinga gas turbine combustor capable of ensuring combustion stabilityimmediately after the load dump of the gas turbine and reducing the NOxemission due to the full speed no-load operation after the load dump canbe realized.

Embodiment 4

Next, the control apparatus of the gas turbine combustor and the controlmethod of the gas turbine combustor of the fourth embodiment of thepresent invention will be explained by referring to FIGS. 9 and 10. Thecontrol apparatus of the gas turbine combustor 2 of the fourthembodiment of the present invention is the same as that of the gasturbine combustor 2 of the first embodiment shown in FIGS. 1 to 3 in thebasic constitution, so that the explanation common to the two is omittedand only the different portions will be explained below.

FIG. 9 shows an entire drawing of the gas turbine unit for powergeneration including the gas turbine combustor 2 which is the fourthembodiment of the present invention and the gas turbine combustor 2 ofthis embodiment, in addition to the constitution of the gas turbinecombustor 2 of the first embodiment, is structured so as to install ableed valve on-off detector 207 for detecting opening or closing of ableed valve 21 installed in the compressor 1 and a logic circuit 208 fordeciding bleed valve on-off signals detected respectively by the bleedvalve on-off detector 207 and the rotating speed detector 200 of the gasturbine and a detection signal of the rotating speed of the gas turbine.

The bleed valve 21 installed in the compressor 1 is installed in themiddle of the flow path for connecting the intermediate stage of thecompressor 1 and the exhaust duct, and the bleed valve 21 is opened, anda part of the compressed air 100 compressed by the compressor 1 ispermitted to escape into the exhaust duct, thus in the start-up andacceleration processes of the gas turbine, the compressor 1 is preventedfrom surging.

The operation of the bleed valve 21, in the start-up and accelerationprocesses of the gas turbine, totally opens the bleed valve 21 and whenthe rotating speed of the gas turbine is at a fixed value or higher,totally closes the bleed valve 21. If the bleed valve 21 is totallyclosed, the flow rate of the compressed air 100 flowing into the gasturbine combustor 2 increases.

Next, the operation of the bleed valve 21 at the time of load dump ofthe gas turbine will be explained by referring to FIG. 10. As therotating speed of the gas turbine, an opening angle 21 a of the bleedvalve 21, and a compressed air flow rate 100 a of the compressor 1 arerespectively shown in FIG. 10, at the time of load dump of the gasturbine, the flow rate of the compressed air 100 flowing into theturbine 3 is reduced and the increase in the rotating speed of the gasturbine is suppressed, so that the opening angle 21 a of the bleed valve21 is controlled so as to be totally opened simultaneously with the loaddump.

Thereafter, if the rotating speed of the gas turbine starts to reduce,the opening angle 21 a of the bleed valve 21 is operated so as to betotally closed. At this time, in accordance with the totally closingoperation of the opening angle 21 a of the bleed valve 21, the flow rate100 a of the compressed air 100 flowing into the gas turbine combustor 2increases, so that when the combustion form of the gas turbine combustor2 is the mixed combustion of the diffusion combustion and premixcombustion, on the downstream side of the premix combustion burner 10,the mixing ratio of fuel and air is lowered, and the premix flame 105formed in the combustion chamber 8 of the gas turbine combustor 2becomes unstable, and there is a possibility of flame loss.

Therefore, until the totally closing operation of the opening angle 21 aof the bleed valve 21 is finished, it is desirable that the gas turbinecombustor 2 is kept in the independent diffusion combustion state ofhigh stability.

Therefore, the control apparatus of the gas turbine combustor 2 of thisembodiment shown in FIG. 9, from the bleed valve on-off detector 207,the gas turbine rotating speed detector 200, and the information of therotating speed of the gas turbine preserved in the recorder 201 forpreserving the information of the rotating speed of the gas turbine,calculates the change with time of the rotating speed of the gas turbineby the rotating speed trend arithmetic unit 202 and checks, by the logiccircuit 8, an on-off signal of the bleed valve 21 detected by the bleedvalve on-off detector 207 and a change with time signal of the rotatingspeed of the gas turbine calculated by the rotating speed trendarithmetic unit 202.

The logic circuit 208, when the condition that the bleed valve 21 istotally closed after the load dump of the gas turbine and the rotatingspeed of the gas turbine starts to reduce is effected, outputs aninstruction signal to the fuel control unit 201.

The fuel control unit 201, upon receipt of the instruction signal fromthe logic circuit 208, so that the combustion form of the gas turbinecombustor 2 is switched from the independent diffusion combustion to themixed combustion of the diffusion combustion and premix combustion,controls so as to reduce the diffusion combustion burner fuel flow rate17 a which is fed to the diffusion combustion burner 9 of the gasturbine combustor 2 via the diffusion combustion burner fuel system 17and increase the premix combustion burner fuel flow rate 18 a which isfed to the premix combustion burner 10 via the premix combustion burnerfuel system 18.

The control apparatus of the gas turbine combustor 2 of this embodimentis structured as mentioned above, thus after completion of the totallyclosing operation of the bleed valve 21 installed in the compressor 1,the combustion form of the gas turbine combustor 2 can be switched tothe mixed combustion of the diffusion combustion and premix combustion.Therefore, by the totally closing operation of the bleed valve 21, thepremix flame 105 formed in the combustion chamber 8 of the gas turbinecombustor 2 can be prevented from becoming unstable and losing theflame.

According to this embodiment, a method and an apparatus for controllinga gas turbine combustor capable of ensuring combustion stabilityimmediately after the load dump of the gas turbine and reducing the NOxemission due to the full speed no-load operation after the load dump canbe realized.

Embodiment 5

Next, the control apparatus of the gas turbine combustor and the controlmethod of the gas turbine combustor of the fifth embodiment of thepresent invention will be explained by referring to FIG. 11. The controlapparatus of the gas turbine combustor 2 of the fifth embodiment of thepresent invention is the same as that of the gas turbine combustor 2 ofthe first embodiment shown in FIGS. 1 to 3 in the basic constitution, sothat the explanation common to the two is omitted and only the differentportions will be explained below.

FIG. 11 shows an entire drawing of the gas turbine including the gasturbine combustor of the fifth embodiment of the present invention andthe control apparatus of the gas turbine combustor 2 of this embodimentis structured so as to install, in place of the rotating speed detector200 of the gas turbine installed in the gas turbine combustor 2 of thefirst embodiment, a timer circuit 209 for transmitting a signal to thefuel control unit 203 after a predetermined period of time from the loaddump of the gas turbine.

According to the control apparatus of the gas turbine combustor 2 ofthis embodiment, the timer circuit 209 receiving the load dump signal ofthe gas turbine transmits a signal to the fuel control unit 203 afterthe predetermined period of time from the load dump.

Namely, the timer circuit 209 is structured so as to preset the timerequired for the rotating speed of the gas turbine to increase once dueto the load dump of the gas turbine to reduce on a level free of troubleeven if the combustion form of the gas turbine combustor 2 is switchedfrom the independent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion and output a signal after thepreset time elapses from the load dump.

And, the fuel control unit 203 receiving the output signal from thetimer circuit 209, so that the combustion form of the gas turbinecombustor 2 is switched from the independent diffusion combustion to themixed combustion of the diffusion combustion and premix combustion,controls so as to reduce the diffusion combustion burner fuel flow rate17 a which is fed to the diffusion combustion burner 9 of the gasturbine combustor 2 via the diffusion combustion burner fuel system 17and increase the premix combustion burner fuel flow rate 18 a which isfed to the premix combustion burner 10 via the premix combustion burnerfuel system 18.

The signal delay time set in the timer circuit 209 should preferably bea sufficient period of time for the rotating speed of the gas turbineincreased from the rated rotating speed due to the load dump of the gasturbine to reduce again down to the rated rotating speed and a shortperiod of time as possible to reduce the NOx emission in the independentdiffusion combustion of the gas turbine combustor 2 and concretely,should preferably be about 30 seconds.

The control apparatus of the gas turbine combustor 2 of this embodimentis structured as mentioned above, thus a similar effect to that of thegas turbine combustor 2 of Embodiment 1 can be reproduced by the simpletimer circuit 209, and the control logic is simplified, thus the cost ofthe control apparatus can be decreased.

According to this embodiment, a method and an apparatus for controllinga gas turbine combustor capable of ensuring combustion stabilityimmediately after the load dump of the gas turbine and reducing the NOxemission due to the full speed no-load operation after the load dump canbe realized.

Embodiment 6

Next, the control apparatus of the gas turbine combustor and the controlmethod of the gas turbine combustor of the sixth embodiment of thepresent invention will be explained by referring to FIGS. 12 and 13. Thecontrol apparatus of the gas turbine combustor 2 of the sixth embodimentof the present invention is the same as that of the gas turbinecombustor 2 of the first embodiment shown in FIGS. 1 to 3 in the basicconstitution, so that the explanation common to the two is omitted andonly the different portions will be explained below.

FIG. 12 shows an entire drawing of the gas turbine unit for powergeneration including the gas turbine combustor 2 that is the sixthembodiment of the present invention and this embodiment is an embodimentwhen the control apparatus of the gas turbine combustor 2 having theaforementioned constitution is applied to a biaxial gas turbine unit.

The biaxial gas turbine unit, as shown in FIG. 12, is a biaxial gasturbine that the axis for connecting the compressor 1 and a highpressure turbine 22 and the axis for connecting the generator 4 and alow pressure turbine 23 are two separated axes.

The gas turbine combustor 2 of this embodiment includes the detector 200for detecting the rotating speed of the gas turbine in the low pressureturbine 23.

FIG. 13 shows, at the time of the load dump of the gas turbine in thecontrol apparatus of the gas turbine combustor 2 of this embodiment, thechanges with time of the diffusion combustion burner fuel flow rate 17 aand the premix combustion burner fuel flow rate 18 a which are fed viathe diffusion combustion burner fuel system 17 and the premix combustionburner fuel system 18 and the changes with time of a turbine rotatingspeed 23 a of the low pressure turbine 23 and a turbine rotating speed22 a of the high pressure turbine 22.

As shown in FIG. 13, in correspondence to the load dump of the gasturbine, the turbine rotating speed 23 a of the low pressure turbine 23connected to the generator 4 increases, so that to suppress the increasein the rotating speed of the low pressure turbine 23, the fuel flow ratefed to the gas turbine combustor 2 is reduced and the combustion form isswitched to the independent diffusion combustion.

The fuel flow rate fed to the gas turbine combustor 2 is reduced, thusthe rotating speed 23 a of the low pressure turbine 23 is slowly reduceddown to the rated rotating speed.

A detection signal of the turbine rotating speed of the low pressureturbine 23 detected by the rotating speed detector 200 is transmitted tothe recorder 201 and the information of the rotating speed of the lowpressure turbine 23 is preserved by the recorder 201. From theinformation of the rotating speed of the low pressure turbine preservedin the recorder 201, the change with time of the rotating speed of thelow pressure turbine is calculated by the rotating speed trendarithmetic unit 202.

When it is detected by the arithmetic unit 202 that the rotating speedincreased immediately after the load dump of the gas turbine starts toreduce due to a reduction in the fuel flow rate, a signal is transmittedto the fuel control unit 203 from the rotating speed trend arithmeticunit 202. The fuel control unit 203 receiving the signal transmittedfrom the rotating speed trend arithmetic unit 202, so that thecombustion form of the gas turbine combustor 2 is switched from theindependent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion, controls so as to reduce thediffusion combustion burner fuel flow rate 17 a which is fed to thediffusion combustion burner 9 of the gas turbine combustor 2 via thediffusion combustion burner fuel system 17 and increase the premixcombustion burner fuel flow rate 18 a which is fed to the premixcombustion burner 10 via the premix combustion burner fuel system 18.

The high pressure turbine 22 serves as a function of driving thecompressor 1, so that the fuel flow rate reduces after the load dump ofthe gas turbine, thus the rotating speed reduces slowly. Therefore, whenthe rotating speed 23 a of the low pressure turbine 23 increases once,then starts to reduce, and approaches the rated rotating speed, so as toswitch the combustion form of the gas turbine combustor 2 from theindependent diffusion combustion to the mixed combustion of thediffusion combustion and premix combustion, increase the diffusioncombustion burner fuel flow rate 17 a and the premix combustion burnerfuel flow rate 18 a which are fed to the diffusion combustion burnerfuel system 17 and the premix combustion burner fuel system 18, andincrease again the rotating speed 22 a of the high pressure turbine 22up to the rated rotating speed, the fuel flow rate is controlled by thefuel control unit 203.

The control apparatus of the gas turbine combustor 2 is structured asthis embodiment, thus even in the biaxial gas turbine unit, thecombustion form can be promptly switched from the independent diffusioncombustion to the mixed combustion of the diffusion combustion andpremix combustion after the load dump of the gas turbine and the NOxemission in the full speed no-load operation state can be reduced.

According to this embodiment, a method and an apparatus for controllinga gas turbine combustor capable of ensuring combustion stabilityimmediately after the load dump of the gas turbine and reducing the NOxemission due to the full speed no-load operation after the load dump canbe realized.

The present invention can be applied to the gas turbine combustor.

What is claimed is:
 1. An apparatus for controlling a gas turbinecombustor having a diffusion combustion burner and a premix combustionburner comprising: a rotating speed detector for detecting a rotatingspeed of gas turbine, a recorder for recording the detected value of therotating speed of gas turbine detected by the rotating speed detector,an arithmetic unit for calculating a change with time of the rotatingspeed of gas turbine in accordance with details of the detected value ofthe rotating speed of gas turbine recorded in the recorder, and a fuelcontrol unit for judging a starting situation of reduction in therotating speed of gas turbine on the basis of the change with time ofthe rotating speed of gas turbine calculated by the arithmetic unit andcontrolling respectively a fuel flow rate for the diffusion combustionburner to be fed to the diffusion combustion burner installed in the gasturbine combustor and a fuel flow rate for the premix combustion to befed to the premix combustion burner.
 2. The apparatus for controlling agas turbine combustor according to claim 1, wherein: the arithmetic unitfor calculating the change with time of the rotating speed of gasturbine is structured so as to detect a situation that the rotatingspeed of gas turbine increased at the time of a load dump of the gasturbine starts to reduce by calculation of the change with time of therotating speed of gas turbine, output an operation signal forcontrolling the fuel flow rate to the fuel control unit, switch, by thefuel control unit, a combustion state of the gas turbine combustor fromindependent diffusion combustion by the diffusion combustion burner tomixed combustion of diffusion combustion and premix combustion by thediffusion combustion burner and the premix combustion burner, andcontrol respectively the fuel flow rate for the diffusion combustionburner fed to the diffusion combustion burner and the fuel flow rate forthe premix combustion fed to the premix combustion burner.
 3. Anapparatus for controlling a gas turbine combustor having a diffusioncombustion burner and a premix combustion burner comprising: a detectorfor detecting a rotating speed of gas turbine, a recorder for recordingthe detected value of the rotating speed of gas turbine detected by therotating speed detector, an arithmetic unit for calculating a changewith time of the rotating speed of gas turbine in accordance withdetails of the detected value of the rotating speed of gas turbinerecorded in the recorder, a bleed valve opening angle detector fordetecting an opening angle of a compressor bleed valve installed in acompressor, a logic circuit for checking a value of the change with timeof the rotating speed of gas turbine calculated by the arithmetic unitand an opening angle signal of the bleed valve detected by the bleedvalve opening angle detector, and a fuel control unit for respectivelycontrolling a fuel flow rate for the diffusion combustion burner to befed to the diffusion combustion burner installed in the gas turbinecombustor and a fuel flow rate for the premix combustion to be fed tothe premix combustion burner so as to switch a combustion state of thegas turbine combustor from independent diffusion combustion by thediffusion combustion burner to mixed combustion of diffusion combustionand premix combustion by the diffusion combustion burner and the premixcombustion burner on the basis of check results by the logic circuit. 4.The apparatus for controlling a gas turbine combustor according to claim3, wherein the control unit of the gas turbine combustor is structuredso that: when it is detected by the checking by the logic circuit thatthe rotating speed of gas turbine increased from a rated rotating speedat the time of a load dump of the gas turbine starts to reduce and theopening angle of the bleed valve installed in the compressor is totallyclosed, the logic circuit transmits an instruction signal to the fuelcontrol unit, switches the gas turbine combustor from the independentdiffusion combustion by the diffusion combustion burner to the mixedcombustion of the diffusion combustion and the premix combustion by thediffusion combustion burner and the premix combustion burner, andrespectively controls the fuel flow rate for the diffusion combustionburner fed to the diffusion combustion burner and the fuel flow rate forthe premix combustion fed to the premix combustion burner.
 5. Anapparatus for controlling a gas turbine combustor having a diffusioncombustion burner and a premix combustion burner comprising: a fuelcontrol unit for respectively controlling a fuel flow rate for thediffusion combustion burner to be fed to the diffusion combustion burnerinstalled in the gas turbine combustor and a fuel flow rate for thepremix combustion to be fed to the premix combustion burner so as toswitch a combustion state of the gas turbine combustor from independentdiffusion combustion by the diffusion combustion burner to mixedcombustion of diffusion combustion and premix combustion by thediffusion combustion burner and the premix combustion burner on thebasis of a signal transmitted from a timer circuit, which is installedto transmit a signal for controlling the fuel control unit after apredetermined period of time after receipt of a load dump signal of gasturbine, after a predetermined period of time.
 6. The apparatus forcontrolling a gas turbine combustor according to claim 1, wherein: thecontrol unit of the gas turbine combustor is installed in a biaxial gasturbine unit.
 7. A method for controlling a gas turbine combustorincluding a diffusion combustion burner and a premix combustion burner,comprising the steps of: detecting a rotating speed of gas turbine,recording the detected value of the rotating speed of gas turbine,calculating a change with time of the rotating speed of gas turbine inaccordance with details of the recorded detected value of the rotatingspeed of gas turbine, judging a starting situation of reduction in therotating speed of gas turbine on the basis of the calculated change withtime of the rotating speed of gas turbine, and regulating a fuel flowrate fed to the gas turbine combustor controls respectively a fuel flowrate for the diffusion combustion burner to be fed to the diffusioncombustion burner installed in the gas turbine combustor and a fuel flowrate for the premix combustion to be fed to the premix combustionburner.
 8. The method for controlling a gas turbine combustor accordingto claim 7, wherein: the calculating a change with time of the rotatingspeed of gas turbine is performed in a situation that the rotating speedof gas turbine increased at the time of a load dump of the gas turbinestarts to reduce by calculation of a trend of the change with time inwhich the rotating speed of gas turbine is recorded and when it isjudged that the situation that the rotating speed of gas turbine startsto reduce occurs, outputting an operation signal for controlling thefuel flow rate to the fuel control unit, regulating the fuel flow ratefed to the gas turbine combustor switches a combustion state of the gasturbine combustor from independent diffusion combustion by the diffusioncombustion burner to mixed combustion of the diffusion combustion andthe premix combustion by the diffusion combustion burner and the premixcombustion burner, and respectively controlling the fuel flow rate forthe diffusion combustion burner to be fed to the diffusion combustionburner and the fuel flow rate for the premix combustion to be fed to thepremix combustion burner.
 9. A method for controlling a gas turbinecombustor including a diffusion combustion burner and a premixcombustion burner, comprising the steps of: detecting a rotating speedof a gas turbine, recording the detected value of the rotating speed ofgas turbine, calculating a change with time of the rotating speed of gasturbine in accordance with details of the recorded detected value of therotating speed of gas turbine, detecting an opening angle of acompressor bleed valve installed in a compressor, and regulating a fuelflow rate fed to the gas turbine combustor on the basis of check resultsof a calculated value of the change with time of the rotating speed ofgas turbine and a detected opening angle signal of the bleed valverespectively controls a fuel flow rate for the diffusion combustionburner to be to the diffusion combustion burner installed in the gasturbine combustor and a fuel flow rate for the premix combustion to befed to the premix combustion burner so as to switch a combustion stateof the gas turbine combustor from independent diffusion combustion bythe diffusion combustion burner to mixed combustion of the diffusioncombustion and the premix combustion by the diffusion combustion burnerand the premix combustion burner.
 10. The method for controlling a gasturbine combustor according to claim 9, wherein: when it is detected bythe checking that the rotating speed of gas turbine increased from arated rotating speed at the time of a load dump of the gas turbinestarts to reduce and the opening angle of the bleed valve installed inthe compressor is totally closed, the fuel control unit for regulatingthe fuel flow rate fed to the gas turbine combustor switches the gasturbine combustor from the independent diffusion combustion by thediffusion combustion burner to the mixed combustion of the diffusioncombustion and the premix combustion by the diffusion combustion burnerand the premix combustion burner and controls respectively the fuel flowrate for the diffusion combustion burner fed to the diffusion combustionburner and the fuel flow rate for the premix combustion fed to thepremix combustion burner.
 11. A method for controlling a gas turbinecombustor having a diffusion combustion burner and a premix combustionburner, comprising the steps of: controlling a fuel flow rate for thediffusion combustion burner to be fed to the diffusion combustion burnerinstalled in the gas turbine combustor and a fuel flow rate for thepremix combustion to be fed to the premix combustion burner respectivelyso as to switch a combustion state of the gas turbine combustor fromindependent diffusion combustion by the diffusion combustion burner tomixed combustion of the diffusion combustion and the premix combustionby the diffusion combustion burner and the premix combustion burner onthe basis of a signal transmitted from a timer circuit, which isinstalled to transmit a signal for controlling the fuel control unitafter a predetermined period of time after receipt of a load dump signalof gas turbine, after a predetermined period of time.
 12. The method forcontrolling a gas turbine combustor according to claim 7, wherein: thecontrol method of gas turbine combustor is used for a control method ofa gas turbine combustor of a biaxial gas turbine unit.